TAMPA — Marijuana is not medicine, Dr. Eric Voth noted Monday night. Doctors cannot control the dose or its possibly toxic side effects, the internist told an audience at the University of Tampa gathered for a debate over medical marijuana.

If it were called "Substance X," any doctor who told a patient to smoke it until they felt better would be committing malpractice, he said.

Orlando attorney John Morgan took up the counterpoint, arguing that marijuana is a natural substance that can ease suffering for hundreds of thousands of Floridians.

"I don't know why it works, but it does,'' Morgan said. "I don't know why water works either, but I trust it.''

Those contrary views represented early salvos as the campaign to legalize medical marijuana in Florida shifts from petition gathering to voter persuasion.

Morgan, who spent about $4 million to get a constitutional amendment on the November election ballot, has become the dominant public face of medical marijuana in Florida. Also arguing in favor of the proposed amendment was Allen St. Pierre, executive director of NORML, which has long advocated for full legalization of recreational pot.

Only the states of Colorado and Washington allow pot for nonmedical use. Polls show that Floridians strongly favor medical marijuana, but oppose full legalization. Morgan usually tries to distance himself from the likes of NORML.

On Monday, beneath the glare of TV cameras, Morgan nearly recoiled when St. Pierre introduced himself.

"I'm on your side,'' St. Pierre said.

"You're on my side?'' Morgan responded. "You are for legalization.''

"Don't worry. We won't get into that much,'' said St. Pierre.

But Voth, chairman of the Institute on Global Drug Policy, a subsidiary of St. Petersburg's Drug Free America Foundation, was only too glad to raise the specter of legalization, referring frequently to the "drug lobby'' and "special interests.''

"Make no mistake,'' Voth told the crowd of about 300, "The end game is legalization.''

The proposed amendment would allow people with chronic debilitating conditions to use marijuana if a licensed doctor recommends it in writing. The pot would be sold at state regulated dispensaries.

Kevin Sabet, director of the Institute on Drug Policy at the University of Florida, joined Voth in arguing against the amendment, saying it is too loosely drawn. Anyone of any age could get pot for any reason, according to the ballot language, he said, echoing those who believe the word "debilitating'' is too vague. Florida, notorious for opiate-based pill mills, will then end up with pot mills as well, he said.

Chemical substances found in marijuana can indeed have medical uses, Sabet said, but drug companies are starting to develop derivatives in safe pill form so patients don't have to rely on pot purveyors with no medical or scientific training.

At times, the debate grew heated and personal. Sabet advised the last three presidents on drug policy and spoke of how the UF institute is devoted to combating drug abuse. Morgan accused Sabet of making a living by opposing marijuana initiatives all over the country, or "selling fear.''

Sabet accused Morgan of twisting facts, "which I guess is a virtue in your profession.''

St. Pierre predicted that the amendment, which would require a 60 percent or better vote to pass, is a done deal. "This is about personal freedom and self-preservation,'' he told a mostly appreciative crowd. "And you can't win in America when you fight personal freedom and self-preservation.''

There is a reason why the air in Tampa Bay is filled with playoff talk. If Thursday night's 12-8 Bucs preseason win over the Jaguars is any indication, it's also going to be filled with footballs thrown by quarterback Jameis Winston.